Portable electronics devices such as digital and film cameras, notebook computers, and onboard vehicular computers containing data storage devices such as hard disk drives are often dropped, bumped, or bounced. When an object is dropped or falls back to earth after a bounce, the object experiences free fall, a period of minimal or zero gravitational force. ‘Free fall’ produces a change in the force, i.e. acceleration, of gravity as perceived in the frame of reference in which the data storage device is at rest. On earth, free fall usually immediately precedes an impact with a surface that may damage operating or unparked data storage devices, their spinning disks, actuators, and read/write heads. A parked data storage device is one in which the actuator has temporarily moved the head away from the spinning disk, and the actuator and head are safely locked in a fixed position in preparation for transportation or an anticipated impact. Because a data storage device can be safely prepared for an impact in a time shorter than the time it takes the data storage device to complete its fall, the present invention has great utility in preventing or mitigating the damage formerly experienced by data storage devices that were dropped down stairs, dropped onto concrete, asphalt or other hard surfaces, or that were bounced into the air from vehicles contacting speed bumps, waves, or turbulent air pockets at high speeds and slammed back down again.
In simplest form, a data storage device, such as a disc drive, consists of a spinning disk and an actuator movably positioned near the surface of the disk. The surface of the disk typically contains multiple annular tracks or grooves in which data is stored and manipulated and from which data is retrieved by a read/write head (e.g. a magnetic or an optical head) positioned on the actuator.
It is important that the data storage head be kept as free from vibrations and/or sudden acceleration or deceleration as possible because the head reads data from and writes data to the multiple annular tracks on the spinning disk. Sudden acceleration or deceleration or excessive vibration of the disk drive can cause the head to skip tracks, to encode information incorrectly on the wrong track or tracks, to erase data previously encoded on the disk, or to dent the disk surface. Several types of sensors have been developed to mitigate or to prevent excessive vibration from harming recorded data, but no sensors measuring changes in the force, i.e. acceleration, of gravity in the frame of the data storage device, existed prior to conception and development of this invention.
One type of vibration detection and protection system found in the field of data storage devices is known as the off track signal or OTS. Generated by an electrical component of a data processing system, such as a magnetic hard disk, or CD, or DVD drive, the OTS is derived from the signals generated by the magnetic hard disk or CD head as it follows data tracks on the disk. The amplitude of the OTS is designed to vary in direct proportion to the amount of vibration experienced by the data processing system. Thus, the more vibration experienced by the data processing system, the more the amplitude of the OTS increases. The system electronics of the data storage device monitors the amplitude of the OTS and temporarily disables the ability of the head to write and/or read information to or from the data storage device whenever the OTS amplitude matches or exceeds a predetermined amplitude.
Although the OTS system protects data stored on the data storage device from being erased or overwritten by the head, it does not prevent damage resulting from the head popping up and down onto the spinning disk when the data storage device is dropped and impacts a surface. For example, if the head slams downward onto a spinning data medium device, such as a CD or DVD or magnetic hard disk, data may be irretrievably lost, the head may be severely damaged, and the CD, DVD, or magnetic hard disk may be irreparably dented.
A second kind of sensor is found in the unrelated automobile field. Sensors in this field are used to deploy various safety devices, such as airbags, whenever an accident occurs. Such sensors passively wait for an impact to occur and then rapidly deploy safety devices before a human's body impacts hard, bone-crushing surfaces within the automobile's interior cabin such as dashboards, windshields, and steering wheels. They cannot predict the possibility of an imminent impact, nor can they detect the absence of a gravitational field as some embodiments of the present invention can. Moreover, sensors found in the automobile field have not been used to protect data in data processing systems such as hard disk drives.
A third type of vibration countermeasure found in the field of consumer portable electronic devices is specifically designed to combat the “skips” commonly associated with audio playback of CD-ROMS and DVD's. “Skips” are miniature, but discernable, periods of silence in music or other audio broadcast material that occur whenever a musical playback device is jostled, vibrated, or dropped. This countermeasure is typically called a “buffering system.” In simplest form, a buffering system incorporated within a musical playback device reads audio data from the spinning disk during playback of the disk at a rate slightly faster than the rate at which the audio data is broadcast. By reading “ahead” of the broadcast, a portion of the audio data is continually saved up and stored in the buffer. Whenever a “skip” occurs, the buffering system ensures a smooth, unbroken audio playback by filling the “skip” with audio data from the buffer. Unlike, the present invention, however, the buffering system does not protect the data storage device or its data actuating head from damage caused by dropping or vibrating the device.